The present invention relates to electrical machines and more particularly a design and method of manufacture for electric motors specifically a stator pole assembly.
Electric motors and generators have a stationary element, termed a stator and movable or rotating elements termed a rotor. The interaction between the stator and the rotor is caused by the interaction on a magnetic field generated by either the stator or the rotor. Such magnetic field is usually generated or induced by electric currents in a winding on either the stator or the rotor or both. Such winding usually comprises a plurality of coils wound around a winding support. The winding support is usually comprised of a soft magnetic material which traditionally is made of laminations of selected steel materials. The laminations are insulated from each other in order to reduce eddy currents. The rotational forces on the rotor about the axis of the rotor are a function of the interaction of the stator and rotor magnetic fields. The forces are generated at a radial distance from the axis generating torque on the rotor resulting from the force of the interaction and the moment arm of the rotor. The moment arm is calculated by the redial displacement of the magnetic field of the rotor with respect to the axis of the rotor.
One concern in the design of such electrical motors is the need or desire to reduce the free space by improving to fill factor of the segments. It is desirable that the segments fill as much of the open space is practical to improve the interaction between the electromagnetic field between the stator in the rotor this produces a more efficient motor generator. Such terminology is deemed as the power density of the motor.
It's become known to replace laminated steel materials of the stator or rotor cores with ferro magnetic powder particles. These ferro magnetic particles are compacted in a powder metallurgy operation to form the winding support. The ferro magnetic power particles themselves are electrically insulated from each other so the resulting compacted product exhibits a low eddy current loss in a manner similar to the use of stacks of laminated steel materials. Such use of compacted metal particles comprised of ferro magnetic powder particles for cores electrical machines is disclosed in U.S. Pat. Nos. 6,956,307 B2, 6,300,702 B1 and 6,441,530 B1.
Prior art motor designs use a significant amount of air space and can be large and heavy when assembled making shipping the assembled electric motor costly. When installing or maintaining, prior art motors require special handling due to the size and weight. Furthermore, prior art motors are not designed to be modular and capable of being broken down to separately shipped components. Design changes to the motor also often require motor manufacturers to retool a facility to manufacture a different design. Retooling is generally very expensive and requires down time from production while the tooling is modified or replaced.
Conventional prior art motors use large amounts of copper in the windings to form each pole of the stator. The magnetic field generated is related to the amount and placement of the copper as well as the current in the windings. Power density may be increased by increasing the effective use of the copper and maximizing the inner surface area of the stator. Increasing the power density of the motor may also be accomplished by forming a modular shaped segment from the ferro magnetic particles to conform the electric motor to the space available.
Prior art motors also require the removal and complete disassembly in order to maintain or repair the stator. There is a need for a modular motor design that may be shipped in segments to an installation site wherein each segment can be optimized to generate a magnetic field of predetermined strength by design of the stator face to optimize available mounting space and optimal use of copper windings to conduct current through the stator segment to create such magnetic field and furthermore, allow alternative designs by stacking a predetermined number of segments to form a stator of a predetermined length to generate performance characteristics engineered for a particular application without retooling the motor manufacturing facility.